implemented isValid for Word16

test/Hamming/Word16Spec.hs

@@ -47,8 +47,18 @@ setCheckBitsSpec = describe "setCheckBits" $ mapM_
   ]
 
 isValidSpec :: Spec
-isValidSpec = describe "isValid" $
-  return ()
+isValidSpec = describe "isValid" $ mapM_
+  ( \(desc, code, expected) -> context desc $ let
+    actual = isValid code
+    in it ("should be " ++ show expected) $
+      actual `shouldBe` expected
+  )
+  [ ( "all zeroes",     0,           True  )
+  , ( "all ones",       0xffff,      True  )
+  , ( "valid",          withChkBits, True  )
+  , ( "no check bits",  noChkBits,   False )
+  , ( "bad check bits", badChkBits,  False )
+  ]
 
 correctErrorsSpec :: Spec
 correctErrorsSpec = describe "correctErrors" $